Controlling matter within nanochannels at atomic scale resolution is crucial for a wide variety of applications, including desalination devices and other types of chemical separations, deposition of quantum dots and molecule-by-molecule deposition, in general, of organic and inorganic molecules, fabrication of nanoscale devices at molecular resolution, precise DNA recording, precision movement of DNA and other biopolymers and other polymers, control of chemical reactions molecule-by-molecule, angstrom-scale movement of macroscale objects, and enabling new interactions between molecules within nanochannels and external particles or polarons, excitons or other types of quasiparticles. Flow through nanochannels is a crucial component of a wide variety of applications for which tunable transport properties are advantageous. For example, flow through nanochannels is a crucial component of a wide variety of applications for which a molecule from a solution is selectively transported with low energy input.
Nanoscale channels are not simply miniaturized microscale channels. However, in prior art methodologies, the transport is assumed continuous as in a pipe, and can not be discretely metered by the attributes of the nanochannel and transported molecules. In conventional methodologies, the substance being transported is treated as having a homogeneous density along the nanochannel.
In the conventional treatment of a single-file of molecules, the prediction in some cases is that there would be no transport, as predicted by the no-slip boundary condition. In other cases, in which a slip coefficient is introduced, the transport, at each instant in time, is constant at each cross section.
The delivery of large molecules by flow external to the nanotube has been numerically simulated (Patra and Král, J. Am Chem. Soc. 133: 6146 (2011), while the transport of charged molecules on the outside of nanotubes has been numerically simulated (Král and Wang, Chem. Rev. 113: 3372 (2013)).
Prior fabricated nanochannel devices have employed nanochannels with of a width where several of the atoms or molecules that enter the channels can fit within the cross section of the nanochannel. In contrast, reports of partially filled narrow nanochannels, for example (5, 3) carbon nanotubes, are relatively recent (Qin et al., Nano Lett. 11:5 (2011); Cambre et al., Phys. Rev. Lett. 104:20 (2010)).
While bulk water freezes near 0 degrees C. at standard pressure (1 atm), water within narrow carbon nanotubes is observed in numerical simulation in a solid-like state at higher temperatures (Wang et al., Science 322:5898 (2008)). The structure of contained frozen water is thought to depend on channel diameter. Wang et al. do not consider transport through nanochannels.
In prior art computer simulations, short single-file nanochannels are simulated being used for desalination (Corry, J Phys. Chem. B 112:5 (2008), Kalra, Garde and Hummer, Proc. Natl. Acad. Sci. USA 100: 10175 (2003)). In fluids applications, such as lab-on-a-chip devices, conventional methodologies suggest that channel lengths should be minimized to reduce power requirements. Additionally, in prior art channels wider than those for single-file flow are used for desalination. The use of wider channels is thought to always increase the volumetric flow rates of water. Molecular groups at the channel entryway hinder the entry of ions into the large channels (Majumder et al., J. Memb. Sci. 316:1-2 (2008)). There, wide channels are used to increase the volumetric flow rates of water. In prior art, nanochannels are modeled as pipes (Majumder et al., Nature 438:7064 (2005); Holt et al., Science 312:5776 (2006)).
In prior art, single-file substances within nanochannels are assumed to be essentially incompressible. In some prior simulations and theoretical models (Berezhkovsky and Hummer, Phys. Rev. Lett. 89:6 (2002); Zhu et al., Biophys. J. 85:1 (2003)), contained substances span the full length of single-file nanochannels and are treated as an incompressible rod. References are made to the collective motion of the particles and “collectivity”, as is appropriate for rod-like motion. In other treatments (Chou, Phys. Rev. Lett. 80:1 (1998)), the atoms or molecules making up the contained substance occupy discrete sites within the nanochannel, or such sites may be unfilled. Thus, contained substances form contiguous incompressible segments spanning sequentially filled sites, which are separated from each other by any number of discrete contiguous vacancies. Contiguous segments are rod-like and the spacing between neighboring substance particles is uniform.
In conventional methodologies, it is considered to be desirable to decrease the roughness in order to increase flow. U.S. Pat. No. 7,341,651 B2 (2008) to Regan et al. proposed to use an electric field to move molecules along a carbon nanotube; however, the carbon nanotube of Regan et al. does not include precise and controllable step-like advance. Regan et al. state that the transport occurs “without the atoms (or clusters of atoms) being . . . stuck on the channel.” For materials that are solid at the operating temperature, Regan et al. propose a means to heat the material, and state “it is necessary that the channel be sufficiently warm to permit atomic movement”. Thus heating is considered advantageous. The device of Regan et al. is limited to charged molecular materials.
Ghosh et al., Science 299:1042 (2003) investigated the flow of water past a bundle of carbon nanotubes and speculated that there is a coupling between the induced voltage and the external classical Poiseuille flow. The generation of a voltage difference in a 1.6 nm carbon nanotube on application of a current in the presence of external water vapor was investigated by Zhao et al., Adv. Mat. 20:1772 (2008).
There is a need to more advantageously provide means to control, adjust, and tune the flux of water or other atoms, molecules, ions, electrons, or other types of particles, through nanochannels. Nanochannels may be used to transport substances while excluding other substances. The ability of nanochannels to allow passage of particular substances while excluding others, is the basis for a variety of applications. For example, water can be allowed passage while excluding sodium, chlorine and other ions, and so these types of nanochannels can be used for desalination.